Thermoplastic net-like webs including cross-laminated webs formed from two or more layers of network structures having the same or different configurations provide webs which can have high strength and tear resistance in more than one direction. Such webs have been found useful for reinforcing materials such as paper products, films, foils and others.
Spunbond processes can produce polymeric nonwoven webs by extruding a multiplicity of continuous thermoplastic polymer strands through a die in a downward direction onto a moving surface where the extruded strands are collected in a randomly distributed fashion. The randomly distributed strands are subsequently bonded together by thermobonding or needlepunching to provide sufficient integrity in a resulting nonwoven web of continuous fibers. One method of producing spunbond nonwoven webs is disclosed in U.S. Pat. No. 4,340,563. Spunbond webs are generally characterized by a relatively high ratio of strength to basis weight, isotropic strength, high porosity and abrasion resistance properties but generally are nonuniform in properties such as basis weight, coverage and appearance.
A major limitation of multilayer composites and laminates containing spunbond nonwoven webs is that the spunbond nonwoven web is typically not uniform in coverage and basis weight. In many applications, attempts are made to compensate for poor fabric aesthetics and limited or variable physical properties that result from this nonuniformity of coverage and basis weight by using spunbond webs that have a heavier basis weight than would normally be required by the particular application if the web had a more uniform coverage and basis weight. This, of course, adds to the cost of the composite product and contributes undesirable features to the composite such as stiffness and bulk.
In view of the limitations of spunbond nonwoven webs in multi-layer composites and laminates, there is a need for improved nonwoven web composites and, particularly, those wherein at least one layer of a self-bonded, fibrous nonwoven web having very uniform basis weight and coverage adhered to at least one layer of a cross-laminated thermoplastic net-like web.
U.S. Pat. No. 3,957,554 discloses a method for attaching plastic nets to nonwoven blankets without the use of adhesives.
U.S. Pat. No. 4,929,303 discloses a breathable polyolefin film laminated to a nonwoven cross-laminated open mesh fabric suitable as a housewrap.
U.S. Pat. No. 4,656,082 discloses a laminate material suitable for use in place of a safety mesh used in construction of roofing which has at least one inner layer of a woven material or an equivalent cross-laminated airy fabric adhesively bonded to each adjacent layer.
U.S. Pat. No. 4,052,243 discloses a method for producing a cross-laminated cloth-like product from wide warp and weft webs composed of fibers, filaments or yarns of organic or inorganic origin.
The patents described above do not disclose the invented self-bonded nonwoven web and cross-laminated thermoplastic net-like web composites comprising at least one layer of a uniform basis weight self-bonded, substantially randomly disposed, substantially continuous thermoplastic filaments fibrous nonwoven web comprising a high degree of basis weight uniformity to which is bonded at least one layer of a cross-laminated thermoplastic net-like web.
An object of the present invention is to provide improved composite fabric structures.
Another object of the present invention is to provide an improved self-bonded nonwoven web composite structure comprising at least one layer of a uniform basis weight self-bonded, fibrous nonwoven web having a plurality of substantially randomly disposed, substantially continuous thermoplastic filaments adhered to at least one layer of a thermoplastic net-like web.
The objects of the present invention are attained with a self-bonded nonwoven web and thermoplastic net-like web composite comprising,
at least one layer of a uniform basis weight self-bonded, fibrous nonwoven web comprising a plurality of substantially randomly disposed, substantially continuous thermoplastic filaments wherein the web has a Basis Weight Uniformity Index (BWUI) of 1.0.+-.0.05 determined from average basis weights having standard deviations of less than 10% and is adhered to
at least one layer of a thermoplastic net-like web.
The objects of the present invention are further attained with a self-bonded nonwoven web and cross-laminated thermoplastic net-like web composite having a basis weight of about 0.2 oz/yd.sup.2 or greater comprising,
at least one layer of a uniform basis weight self-bonded, fibrous nonwoven web having a basis weight of about 0.1 oz/yd.sup.2 or greater and a BWUI of 1.0.+-.0.05 determined from average basis weights having standard deviations of less than 10% comprising a plurality of substantially randomly disposed, substantially continuous thermoplastic filaments wherein the filaments have deniers in the range of about 0.5 to about 20 and comprise a thermoplastic selected from the group consisting of polypropylene, a random copolymer of propylene and ethylene, and a blend of polypropylene and polybutene or linear low density polyethylene wherein the layer is adhered to
at least one layer of a cross-laminated thermoplastic net-like web having a basis weight of about 0.1 oz/yd.sup.2 or greater comprising a thermoplastic selected from the group consisting of polyolefins, combinations of polyolefins, and polyesters.
The objects of the present invention are still further attained with a self-bonded nonwoven web and cross-laminated thermoplastic net-like web composite having a basis weight of about 0.4 oz/yd.sup.2 or greater comprising,
at least one layer of a uniform basis weight self-bonded, fibrous nonwoven web having a basis weight of about 0.1 oz/yd.sup.2 or greater and a BWUI of 1.0.+-.0.05 determined from average basis weights having standard deviations of less than 10% comprising a plurality of substantiality randomly disposed, substantially continuous thermoplastic filaments wherein the filaments comprise a thermoplastic selected from the group consisting of polypropylene, a random copolymer of propylene and ethylene and a blend of polypropylene and polybutene or linear low density polyethylene,
a layer of a cross-laminated thermoplastic net-like web having a basis weight in the range of about 0.1 oz/yd.sup.2 or greater comprising a thermoplastic selected from the group consisting of polyolefins, combinations of polyolefins and polyesters, and
a layer of a polymeric coating composition having a basis weight of about 0.2 oz/yd.sup.2 or greater comprising a composition selected from the group consisting of ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer and linear low density polyethylene located between and integrally adhered to the self-bonded nonwoven web layer and the cross-laminated thermoplastic net-like web layer.
Among the advantages obtained from the self-bonded nonwoven web and cross-laminated net-like web composites of the present invention are improved strength and stability, in both machine and transverse directions, and lower basis weights. These improvements are achieved due to the very uniform basis weight property of the self-bonded, fibrous nonwoven webs comprising a plurality of substantially randomly disposed, substantially continuous thermoplastic filaments together with the excellent machine and cross machine direction strength and flexibility of the net-like web. The very uniform basis weight of the self-bonded web enables a lower basis weight self-bonded web to be used compared with other materials such as spunbond fabrics and the like to provide coverage to the composites. The uniform basis weight and coverage of the self-bonded nonwoven web also enables lower basis weight polymeric coating compositions to be used to bond cross-laminated thermoplastic net-like webs to the self-bonded nonwoven webs. The use of blends of polypropylene and polybutene and/or linear low density polyethylene provides the self-bonded nonwoven web layers of the composites with a softer fabric hand such that the nonwoven webs have greater flexibility and/or less stiffness.